There are two markets for books (and music).
The first market consists of grazers, collectors, or omnivores. They make the market happen. They read a lot of books. They visit the library often. They have 2,000 LPs in their collection. They listen and read around the edges.
The second market consumes in response to the market. The average American buys just over one book a year. When I was in college, the typical dorm room had just 40 LPs stacked up. (Even today, when students have 100,000 mp3s, most of them don’t listen widely.)